Sweep circuit for cathode ray tube distributors



March 10, 1942. R. E. MATHEs SWEEP CIRCUIT FOR CATHODE RAY TUBEDISTRIBUTOR Filed Feb. 28, 1939 -2 Sheets-Sheet l NN n @md L INVENTOR. IR/CHA D E. MATHES BY )7&6

' ATTORNEY.

March 1.0, 1942. R E MATHES 2,275,974

SWEEP CIRCUIT FOR CATHODE RAY TUBE DISTRIBUTOR` v Filed Feb. 28, 1939 2Sheets-Sheet 2 I Il".

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Patented Mar. 110, 1942 ySVVEEP CIRCUIT FOR CATHOIDE )RAY TUBEDESTRIBUTRS Richard E. Mathes, Westfield, J., assigner to RadioCorporation of America, a corporation of Delaware Application FebruaryZ8, 1939, Serial No. 258,870

1-3 Claims.

This vinvention relates to sweep circuits for cathode ray tubedistributors. Electronic distributors are well known in the art. Sometypes of these distributors comprise a cathode ray tube having an arrayof targets against which an electron bea-m is projected by an electrongun. The beam itself is deflected so as to impinge successively ondifferent targets. A preferred system is one in whichthe targets arearranged in'a circle and the beam is deected in a rotary path over thesegmentary targets thereby to control different external circuits. Aprimary use for such a system of distribution is in the communicationsfield where multiplex telegraph channels are involved. When theapparatus of my invention is so used, the cathode ray tube distributorconstitutes a substitute for any of the well known types ofdistributors, which include face plates and brushes rotating thereover,'or which comprise cam operated contact springs.

It is an object of my invention to provide a novel sweep circuit forcontrolling the deflection of an electron beam in a cathode ray tube.

It is a further object of my invention to provide a cathode ray tube andassociated circuits suitably adapted for use as a multiplex distributorin a telegraph system.

Further objects and advantages of my invention will be set forth in thefollowing detailed description. The description itself will be madeclear by reference to the accompanying drawings, in which:

Figure 1 shows schematically a preferred circuit arrangement includingvarious elements in combination for carrying out the objects. of theinvention; and I Fig. 2 shows an alternative embodiment of the s-ystem.

One ofthe problems encountered in designing a suitable sweep circuit forthe control of a cathode ray tube which is to be employed in a-mu1tipleX telegraph system is to produce beam deflection in a rotary path ata relatively slow speed. In practice it may be necessary to provide atwophase current of 'sine wave characteristic the frequency of whichmust be maintained constant at as low a value as one or even one-halfcycle per second. It is apparent that ordinary methods of oscillationgeneration and coupling of circuits for the transfer of energy at such alow frequency would involve special considerations. A pure sine Wave ofsuch low frequency would lack the necessary power to energize thedeflecting' coils of the cathode ray tube if developed by ordinarytransformation methods. I have; therefore, resorted to a high audiofrequency `monotone generator as a source of sweep circuit power, andthe output 'from such a generator is suitably 'modulated at the desiredlow frequency, so that, when the high frequency component is filteredout, this low frequency becomes available for actuating the deflectingcoils or electrostatic plates of the cathode ray tube.

Referring first to Fig. 1, I show therein a high frequency oscillator 5which may be of any well known type. Part of the output from thisoscillator is fed to a set of polarizing coils 62 whose cores are hereshown as the four stator 4poles of a rotary machine. The windings 62 areso directed as to render the physically opposedl pole faces opposite ininstantaneous polarity. Another part of the output from the oscillator 5is fed to an armature coil 6. 'I'he armature lpole faces are presentedalternately to the horizontal and vertical poles of the stator field. Apotentiometer 6I is in circuit with the field coils, and anotherpoentiometer 63'is similarly disposed in the armature circuit. Thesepotentiometers can be so adjusted as to neutralize the magnetism inthevertical stator poles in one position of the armature and to producemaximum magnetization thereof when the armature is turned through 180.The same is true of the horizontal stator poles. Currents are,therefore, induced in the coils I2 and I3.

Coils I2 are series-connected to4 a rectifier It, while coils I3 arelikewise series-connected to another rectier I5. The amplitudevariations in" the two circuits have ,a phase difference of 90. Theoutput from the rectiflers is fed to different low pass filters IB andI'l where the high frequency component is filtered out, leaving only the.low frequency component which represents the modulation envelope, orfrequency of rotation of 'Ihe low frequency components of the outputl-from the filtersl I5 and Il are in 90 phase relation to one another sothat the beam in the cathode ray tube is deflected rotatively.

A relay winding 2I is disposed in a telegraph receiving circuit. Thearmature of this relay plays between a positive contact 22 and anegative contact 23 so as to impress positive marking impulses across acondenser 24 and to apply the same to a control grid 25 within thecathode ray tube in response to the reception of marking and spacingimpulses. The positive and negative potentials which are impressed uponthe relay the cathode ray tube by means of a biasing source 29 and aresistor 30. l

Lockingcircuits for` channels A, B, C and D respectively are shown inblock diagram and each in circuit with one of the anode `targets 20 ofthe cathode ray tube. The details of the locking circuits are well knownin the artand are, therefore, not shown in detail herein. An example ofa locking circuit which I have used advantageously in this connection isone that was constructed in accordance with the disclosure of James J.Finch in his United States Patent 1,844,950, granted February 16,1932.It will be understood, however, that these locking circuitsl may becpnnected to any suitable recorders such as R1 Rz R3 and R4, as shown inFig. 1.

In order that synchronism may be maintained between the incoming signalsand the rotation of the rotor .6, a striking impulse generator 50, acommutator I, a synchronous correction circuit 3| and correction motor32` are provided. The striking impulse generator 50 is under control ofthe incoming signals as derived from the receiving relay 2|. Shortimpulses are generatediwith each shift of the armature of relay 2l.Ihese impulses are fed to Ia commutator brush 5I mounted on the shaft 1.When truesynchroin succession and with a 90 phase difference between themoments of maximum energy transfer. In Fig. 2 the same arrangement ofrectiflers I4 and 1I5 and low pass lters I8 and I1 may beA employed aspreviously described in connection with Fig. 1. As a modification of thecircuit arrangement, however," electrostatic deecting plates 43 and 44are shown in place of the deflecting coils I8 and I9'. As a furthermodification, the cathode ray tube distributor comprises only threetarget electrodes 45 each occupying approximately a 120 segment as wouldbe required nism and phase are maintained, the striking impulses areapplied to the brush 5I at the moment of its passage over an insulationgap between twocommutator segments 52 and 53. When the phase of theshaft 1 leads or-,Lags, however, then segment 52 or segment53 receivesthe striking impulse, which is then fed to a correction circuit 3I foractuating a polarized relay therein.

Such correction circuits are wellLknown in the art. They usually.include thermionic devices, as illustrated in my United States Patent2,038,375, granted April 21, 1936.v The polarized relay, though notshown herein, will be understood to control two circuits 54 and 55leading to the field windings of the correction motor 32,. forreversibly actuating the same.

'I'he correction motor 32 has a pinion 33 -mounted on its shaft. Thispinion engages with a gear 34 attached to the field frame of the motorI0. By rotating this field framesuitable phase correction is applied formaintaining the necessary synchronism between the equipment at thetransmitter and that at the receiver.

Accurate phase adjustment of the modulator rotor on which the coil 6 ismounted is obtained by means of a gear reduction whichv includes theworm 9 on the shaft of themotor I0, and a worm wheel 8 on the armatureshaft 1. The motor III is preferably driven by current from a constantfrequency source I I.

Referring now to Fig. 2, I show a modified sweep circuit arrangement fora telegraph' dis-A tributor. Certain of the units therein employed havethe same functions as those of corresponding units shown in Fig. 1. Thesubstitution of these alternative units may be made individually andindependently of one another. A

In place ofv the four-pole modulator system as shown in Fig. 1, I haveshown'an arrangement of doughnut coils in Fig. 2. These coils includefour pairs of stator coils and one pair of rotor nected to the highfrequency oscillator 5. These rotor coils 4I are driven by the motor IIIso as to induce currents in the stator coils 40 and 42 for three-channelmultiplex distribution. Each of the segments is connected to a differentkeyer circuit for channels A, B and C respectively. Anode potential issupplied to the targets 45 of the cathode ray tube from a source 46.

The keyers of Fig. l2 are shown in block diagram since the details ofsuch devices are well known in the .art and do not constitute anypart'of the instant invention.- 'I'he output circuits for these keyersmay, however, be connected in common. to any suitable transmitter suchas that shown diagrammatically at 41 and having an output circuitfeeding to a radio antenna 48.

Any of the alternatively used pieces of equipment such as'shown in Fig.2 may be employed in connection with receiving devices as well as 'inthe art in view of the foregoing description.

The scope of the invention itself is, therefore,

' limited only in accordance with the claims.

I claim:

1. In a telegraph system a source of alternating current of 4,arelatively high frequency, rotary converter` means for applying variableattenuation to said currentI at a relatively low frequency cyclic rate,a pair of output circuits connected to said converter means, means formaintaining a quadrature phasedisplacement between the at. Ytenuationenvelopes of the currents in said output circuits, means for derivingsine wave currents corresponding in frequency to that of saidattenuation envelopes, meansfor deiiecting an electron stream rotativelyunder control of said sine wave currents, and means responsive totelegraph signals for -keying said electron stream.

2. Apparatus according tn claim 1 in combination with an adjustablephase correction device operatively associated with said converter'means, and means responsive to said telegraph signals for adiusting saidphase correction device.

3. In a telegraph system including a device for producing a very 4lowfrequency rotative deflecting torce to be .applied to the deflectingelements of a cathode ray tube, a source of high audio frequencycurrent, cyclically operable means for varying lthe amplitude of saidcurrent, and for producing two envelopes thereof, one of said en'-velopes being in quadrature phase relation to the vothe` of saidenvelopes, rectifying and filtering ducting said telegraph signalsthrough y'the discharge path of said cathode ray tube.

4. In a telegraph system` including a sweep circuit for a cathode raytube distributor, an oscillation generator, means for modulating theoutput energy from said generator thereby to produce two relatively lowconstant frequency envelopes having a 90 phase diierence between theirrespective moments of maximum amplitude, means for rectifyingthemodulated 'ener-l gies, means including a pair of low pass filtersfor deriving 90 phase-displaced sine waves of said low constantfrequency envelopes free from the frequency component of saidoscillation generator, a cathode ray tube having horizontal and verticaldeflecting elements combined therewith,

rotor coils in inductive relation to said stator coils and for causingcurrents of cyclically variable attenuation to be induced in said statorcoils, means .for maintaining a quadrature phase relation between theinstants of like attenuation of the currents induced in the two sets ofstator coils, means for converting said currents into sine wave currentsof a frequency corresponding to the cycles of variable attenuation, autilization device comprising a cathode ray tube having horizontal andvertical beam deflect'ing means operable by one and the other ofsaidsine wave currents respectively to produce rotary beam deiiection,and distributor means in said cathode ray tube for assigning multiplextelegraph signals to their respective channels according to said rotarybeam deection.

6. In a telegraph system including apparatus for applying relativelyslow alternations of elec: tromotive force to the horizontal andvertical de# fleeting means of a cathode ray tube, the method ofdistributing telegraph signals to diierent channels which methodcomprises causing the telegraph signals to control the emission in saidcathode ray tube and totraverse the space path therein, producing arelatively high frequency current, inducing currents of said highfrequency in two separate circuits. causing said induced currents to becyclically attenuated at a frequency corresponding to relatively slowalternations, causing the cycles of attenuation in-one of said circuitsto lag 90 behind corresponding cycles in the other of said circuits,rectifying and filtering said induced currents to producesine waveshaving the frequency of said slow alternations, and utilizing said sineWaves separately to control said horizontal and vertical deecting meansthereby to produce a rotary scanning actionin said tube. Y

7. In a telegraph system, a source ofrelatlvely high frequency waves,means for modulating same relatively low frequency, means for main Caltaining a quadrature phase relation between'the low frequency componentsof the energies thus separately modulated, two rec'tiers each fedrespectively with energy from an appropriate one of said modulatingmeans, a cathode ray tube distributor having a horizontal deflectirigdevice controlled by output energy from one of said rectiers and avertical deecting device controlled by output energy from the other ofsaid rectiers, said distributor having anodal targets arranged to bescanned by an electron beam under` control of said deflecting devicesand means for keying the emission in said distributor of telegraphsignals.

8. Apparatus comprising the combination set by a train forth in claim 7and including twolow-'pass lters, one in circuit with the horizontaldeilectng device and one in circuit with the vertical deflecting device.

9. The method of distributing telegraph signals `to different multiplexchannels by rotative` deflection of an electron beam in a cathode vraytube which comprises generating a relatively high frequency, producingtwo 90 phase-displaced components of a relatively low frequency,separately modulating different portions of said relatively highfrequency' each by one of said lowfrequency components respectively,separately rectifying said modulated portions to derive two'substantially 90 phase-displaced wave trains of said l low frequency,filtering out the residuahhigh frequency components in saidwave trains,applying one of said wave trains for deilction of said beam in ahorizontal direction, and applying the other of said wave trains fordeflection of saidbeam in a vertical direction, and keying the emissionin said cathode ray tube by means of said `two quadrature phase relatedcurrents of said low frequency, an electron discharge device having anelectron gun, beam deilecting means, and

circularly disposed` target electrodes, means including a source oftelegraph signals for impulsively controlling the action of saidelectron gun, and circuits for so feeding said low frequency currents tosaid beam deflecting means as to produce rotative beam deection, therebyto cause successive impulses of electronic emission corresponding tosaid telegraph signals to be distributed/to v appropriate ones of'saidtarget electrodes.

11 An electronic distributor in accordance with claim 10,- incombination with means responsive to saidy telegraph signals forregulating the speed of said modulator.

12. An electronic distributor according to claim 10 and having magneticdeiiecting coils in saidbeam deiiecting means.

13. A51 electronic distributor according to claim 10, and havingelectrostatic deiiecting plates in said beam deflecting means.

, y RICHARD EMATHES.

